I think it's fun to play with. Unfortunately this isn't all that great a tool to convince people that timing the market is hard because you're only making decisions based on price, not based on other factors that people can use to make a decision on whether they should buy or sell (such as P/E ratio).
Yes, a similar game based on a P/E graph could be fun too.
I can't beat this, but I can match it almost every time by just hitting sell and buy as fast as i can right at the start, effectively using the game to index.
Sell your children for cash, facepunch Robert Shiller, and buy, Buy, BUY!!